1. Field of the invention
The invention relates to a self-closing valve assembly for installation in a dispensing opening of a container, a seal cap or the like.
2. Description of the Related Art
A valve assembly of the present type, integrated into a seal cap, is known from DE-A-195 10 007. Therein, a membrane-like closure element of flexible material having a central, permanently open passage-opening is clamped between parts of the seal cap adapted to be screwed onto the neck of a container. In the inoperative state, the closure element is concavely curved and its outer face rests on a sealing element which is held stationary in the cap part in order to seal the passage-opening. The closure element can be lifted off the sealing element by an increased pressure exerted on the closure element applied from the side thereof facing the sealing element so that a medium can flow out along the passage-opening from a container, upon whose neck the seal cap can be screwed. As soon as the pressure force on the closure element is removed, the latter readopts its inoperative position due to the elasticity of the flexible material and thereby seals the passage-opening. On the other hand, the closure element is clamped in the cap part such that the tensional effect enables the entry of air, when a low pressure prevails in the interior of the container, in order to effect pressure balance. The pressure balancing function is thus dependent on how the closure element is clamped in the cap part and may be adversely affected by the elasticity of the closure element and the clamping forces effective thereon, so that the pressure balancing function cannot always be guaranteed. Moreover, the channels, along which the ventilating air can flow for producing the pressure balancing effect, can readily be blocked in use and the pressure balancing function may thereby be lost. It is also disadvantageous that the sealing of the passage-opening in the closure element is effected by means of a rigid, flat sealing element so that the sealing function can easily be adversely affected by deposits or dirt on the sealing surface.
An object of the invention is to provide a self-closing valve assembly of a type referred to above having improved sealing and pressure balancing functions. Another object of the invention is to provide a self-closing valve assembly of a type referred to above which can be more conveniently manufactured than prior self-closing valve assemblies. Still another object of the invention is to provide a self-closing valve assembly of a type referred to above which readily can be miniaturized.